The present invention relates to a steering wheel having an airbag device (an airbag module) for protecting the head and the part near the head of an occupant seated on the driver's seat of a vehicle.
Conventionally, in this type of steering wheel, an airbag device is installed in a central portion of a steering wheel body fixed to a steering shaft of a vehicle (see, for example, Japanese Laid-Open Patent Publication No. 2004-284414). The airbag device has a pad forming an ornamental surface at the center of the steering wheel. A bag holder is attached to the backside of the pad and an airbag is received in the space between the bag holder and the pad in a folded state. A horn plate is arranged in the steering wheel body to face the backside of the bag holder. The horn plate has a fixed portion fixed to the steering wheel body. A plurality of horn switch mechanisms are arranged between the horn plate and the bag holder and support the bag holder.
Each of the horn switch mechanisms includes a bolt, a fixed member, a movable member, and a compression coil spring. The bolt is passed through the horn plate from the steering wheel body and threaded to the bag holder. The bolt is inserted also through the fixed member and the movable member. The coil spring is arranged between the fixed member and the movable member. The fixed member is provided close to the horn plate and has a fixed contact. The movable member is arranged close to the bag holder and has a movable contact. The coil spring urges the movable member toward the bag holder in such a manner that the movable contact is separated from the fixed contact.
In this airbag device, the pad, the bag holder, and the movable members and the bolts of the horn switch mechanisms are integrally movable toward the horn plate against the urging force of coil springs. The backside of the head of each bolt contacts the horn plate. This restricts separation of the bag holder from the horn plate in such a range that the distance between the bag holder and the horn plate does not exceed a predetermined distance, despite the urging force of the coil springs applied to the bag holder. When the pad is pressed toward the steering wheel body, the movable contact of a horn switch mechanism contacts and is electrically connected to the fixed contact. This activates the horn of the vehicle. Further, when the vehicle receives impact, gas is generated in an inflator and inflates an airbag instantly. As a result, the impact acting on the driver is attenuated.
Since the airbag of the above-described steering wheel having the airbag device functions also as the mechanism for activating the horn, the airbag device and the horn mechanisms are configured complicatedly and have a large number of components. In this regard, the conventional steering wheel has plenty of room for improvement.